Quick Explosion: How to give shrapnels hitboxes
You can't fix that with QuickExplosion. 

Since its based on particles, only particle as point (placed in centre of each piece) collides. Maximum you can get is spherical boundary so they stay more above surface, but they will still rotate and boundary will be the same size for all shards = some will levitate some still partialy under surface.
From this answer it seems you can make it better.



To make it work properly you will need to use Rigid Body simulation for shards done with Fracture Cell addon or beter via Fracture modifier (that is not include officially in 2.8x for now).

Some older tips you can find here